The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The HDA includes at least one disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The PCBA includes a disk controller for generating servo control signals. The HSA includes a head for reading and writing data from and to the disk. The HSA is controllably positioned in response to the generated servo control signals from the disk controller to move the head relative to tracks of the disk.
The HSA includes an actuator assembly, at least one head gimbal assembly (HGA), and a flex cable assembly. The actuator assembly typically includes an actuator having an actuator body with one or more actuator arms extending from the actuator body. Each actuator arm supports the HGA that includes a head. An actuator coil is supported by the actuator body. The actuator coil interacts with a magnet to form a voice coil motor. The PCBA controls current passing through the actuator coil that results in a torque being applied to the actuator. The HSA further includes the flex cable assembly in electrical communication with the PCBA. The flex cable assembly supplies current to the coil and carries signals between the head and the PCBA.
A flexure extends along the load beam and is considered a sub-component of the HGA. The head is attached and electrically connected to the flexure. The flexure includes a flexure tail portion that extends away from the head. The flexure tail portion is disposed adjacent the actuator body and attaches with the flex cable assembly. The flexure includes conductive traces that extend from adjacent the head and terminate at electrical connection points at the flexure tail portion. The flex cable assembly includes a flex cable with electrical conduits that correspond to the electrical connection points of the flexure.
The head includes a slider and a transducer disposed on the slider. Several conductive pads are distributed along a trailing side of the slider. The conductive pads are electrically connected to electrical components of the transducer that are disposed on a trailing surface of the slider. Such electrical components may include poles of a writer, shields of a read element, and electrical ground, for examples. The electrical pads are electrically bonded with the conductive traces of the flexure. Standard assignment or ordering of the conductive pads is common. The state of the art flexure design includes not only a gimbal structure that provides compliance necessary for flying the slider, but also includes many conductive traces extending to the flexure tail portion for electrical connection with a preamplifier chip or “pre-amp.”
In many contemporary disk drives, the head includes some electrical connection to ground. Different approaches have been taken to provide such grounding. In one approach, the head is electrically grounded to the flexure, for example, using a conductive epoxy in contact with both the slider body and the flexure, or through a conductive via leading from a transducer terminal to the metal backing layer of the flexure.
In another approach, the head is grounded through a conductive trace leading to a pre-amp. This approach to grounding entails additional complexity and constraints because the pre-amp may be disposed at the flex cable to flexure tail interface at the actuator body, and so the grounding path is constrained by the routing patterns of other needed conductive traces on the flexure. Because the conductive traces are typically disposed in a common plane and cannot cross one another without electrically shorting, there are inherent limitations as to the trace routing patterns. A standard conductive trace routing configuration includes the conductive traces that are to be connected to the innermost pair of the conductive pads being assigned to the outermost traces that extend along the flexure to the pre-amp. As such, ordering of the electrical traces at the conductive pads constrains the ordering of such traces at the pre-amp. Moreover, with smaller form factor disk drives, there is limited area at the flex tail portion and flex cable interface for trace rerouting or re-ordering at such location.
It would be desirable to have more freedom with regard to the pin-out configuration of the flex cable and/or a pre-amp that electrically connects to the flexure tail portion of the flexure, rather than have the pin-out configuration dictated by the standard ordering of the pads on the slider and/or routing limitations of the conductive traces of the flexure. As such, there is a need in the art for an improved flexure configuration to enhance freedom of electrical connectivity between the head and the pre-amp.